Date: Wed, 22 May 2013 14:06:40 -0700 From: Haven Hash <havenster@gmail.com> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: net@freebsd.org Subject: Re: surprise surprise (VM related) [luigi@FreeBSD.org: svn commit: r250911 - head/sys/kern] Message-ID: <CAMUJtRPKmsv9nxS4gSPTZUi1bjvgK03P-TS7D4cEcCt7MNO5Lg@mail.gmail.com> In-Reply-To: <20130522164244.GB95808@onelab2.iet.unipi.it> References: <20130522164244.GB95808@onelab2.iet.unipi.it>
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I notice the commentary by poll_burst_max stating it's suitability to 100Mbit net, perhaps that could use an increase in its default value as well? On Wed, May 22, 2013 at 9:42 AM, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > all that work on paravirtualization (as presented at bsdcan) > > http://info.iet.unipi.it/~luigi/netmap/talk-bsdcan-2013.html > > just to discover that simply enabling DEVICE_POLLING (10-years old > technology) gives the same performance gains plus livelock-avoidance. > > And no, linux's NAPI is nowhere near us. > > cheers > luigi > > > ----- Forwarded message from Luigi Rizzo <luigi@FreeBSD.org> ----- > > Date: Wed, 22 May 2013 16:32:18 +0000 (UTC) > From: Luigi Rizzo <luigi@FreeBSD.org> > Subject: svn commit: r250911 - head/sys/kern > To: src-committers@freebsd.org, svn-src-all@freebsd.org, > svn-src-head@freebsd.org > > Author: luigi > Date: Wed May 22 16:32:18 2013 > New Revision: 250911 > URL: http://svnweb.freebsd.org/changeset/base/250911 > > Log: > Increase the (arbitrary) limit for the number of packets per tick > from 1k to 20k The previous value was good 10 years ago, but not > anymore now. > > More importantly, lots of good surprises: > polling is incredibly effective under virtualization, and not only > prevents livelock but also saves most of the VM exit overhead in > receive mode. > > Using polling, a FreeBSD instance under qemu-kvm remains perfectly > responsive even when bombed with 10 Mpps over an emulated e1000, > and happily processes 1.7 Mpps through ipfw. > > Note that some incompatibilities still remain: e.g. polling is not > (yet) compatible with netmap, and seems to freeze the guest when > kern.polling.idle_poll=1 > > MFC after: 3 days > > Modified: > head/sys/kern/kern_poll.c > > Modified: head/sys/kern/kern_poll.c > > ============================================================================== > --- head/sys/kern/kern_poll.c Wed May 22 15:15:05 2013 (r250910) > +++ head/sys/kern/kern_poll.c Wed May 22 16:32:18 2013 (r250911) > @@ -87,12 +87,11 @@ static struct mtx poll_mtx; > * The following constraints hold > * > * 1 <= poll_each_burst <= poll_burst <= poll_burst_max > - * 0 <= poll_each_burst > * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX > */ > > #define MIN_POLL_BURST_MAX 10 > -#define MAX_POLL_BURST_MAX 1000 > +#define MAX_POLL_BURST_MAX 20000 > > static uint32_t poll_burst = 5; > static uint32_t poll_burst_max = 150; /* good for 100Mbit net and > HZ=1000 */ > > ----- End forwarded message ----- > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >
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